Characteristics of long-duration precipitation events across the United States

Previous studies have indicated that extreme precipitation intensity is increasing over time, and has been attributed to anthropogenic warming. Generally these studies have limited analyses to data from daily rainfall totals. We extend those studies by examining characteristics associated with storms of varying duration. We find that significant differences exist in the character of longduration storms (those of twenty consecutive hours or more) from 1948 to 2004. Specifically we find that, although long-duration storms are becoming wetter, (a) they are occurring less frequently and, consequently, comprising a progressively smaller proportion of the total storm number, and (b) they are contributing a smaller proportion of the total rainfall. Geographically, these storms are more likely to influence the Gulf States (particularly in autumn) and the central west coastal area of northern California. Fundamentally, this study suggests that evaluating precipitation over daily time frames may not capture the full complexities in extreme rainfall events.